Hydrogenative denitrogenation

ABSTRACT

HYDROCARBONS CONTAINING ORGANONITROGEN COMPOUNDS ARE DENITROGENATED BY REACTING HYDROGEN WITH THE HYDROCARBON FEED UNDER DENITROGENATION CONDITIONS IN THE PRESENCE OF A CATALYTIC COMBINATION OF AT LEAST ONE MOLYBDENUM COMPOUND AND AT LEAST ONE GROUP VIII METAL OR METAL COMPOUND PREPARED BY IMPREGNATING A FORAMINOUS REFRACTORY OXIDE SUPPORT WITH A HIGHLY STABLE SOLUTION OF THE METAL COMPOUNDS AND AN ACID OF PHOSPHORUS WHEREIN THE IMPREGNATING SOLUTION HAS A P/M0O3 WEIGHT RATIO OF ABOUT 0.1 TO ABOUT 0.25 AND AN INITIAL PH OF ABOUT 1 TO ABOUT 2.

United States Patent 3,749,664 HYDROGENATIVE DENITROGENA'IIUN Grant A. Michelson, Yorba Linda, Califi, assignor to Union Oil Company of California, Los Angeles, Calif. No Drawing. Continuation-impart of application Ser. N 0. 837,340, June 27, 1969, which is a continuation-in-part of application Ser. No. 761,322, Sept. 20, 1968, both now abandoned. This application Apr. 1, 1971, Ser.

rm. Cl. Clllg 17/00 U.S. Cl. 208254 H 12 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of my c0- pending application Ser. No. 837,340, filed June27, 1969, itself a continuation-in-part of my application Ser. No. 761,322, filed Sept. 20, 1968, both of which are now abandoned.

BACKGROUND The considerable volume of literature published in the area of hydrogenative hydrocarbon conversion over the past several years makes it readily apparent, even upon only cursory investigation, that considerable efiort has been devoted to understanding, defining and improv ing the numerous aspects and characteristics involved in the variety of processes and reaction mechanisms observed in the catalytically promoted reaction of hydrogen with hydrocarbons. Obviously the investigation of catalyst characteristics alone is not sufficient. Quite the contrary, relevant catalyst characteristics such as physical and compositional properties have significance in a commercial context or in most technological contexts with relation to the response that the catalyst exhibits in a given process efivironment. A brief investigation of the literature thus far published on this subject illustrates that the number of process parameters, which should realistically include catalysts compositional and physical characteristics, is almost endless. In addition, the significance of some of these parameters changes in response to changes in other variables. For example, the most highly active gasoline hydrocracking catalysts are not the most highly active midbarrel hydrocracking catalysts. Conversely catalysts which exhibit excellent activity in the absence of nitrogen, sulfur, and/or aromatic compounds often exhibit markedly inferior activity, as compared to other compositions, for hydrocracking feedstocks containing substantiakamounts of these deleterious materials. In other words, the activity and selectivity of a given catalyst must be determined not only in relation to the particular conversions desired, i.e., gasoline hydrocracking, midbarrel hydrocracking, denitrogenation, desulfurization, olefin hydrogenation, aromatics hydrogenation and the like, but must be evaluated in view of the system in which the catalyst is expected to perform these objectives.

Obviously all of the problems involved in this area of technology have not yet been solved nor are the several process parameters which compliment or mitigate ice against the desired objectives completely understood. Consequently, the continuing development of hydrogenative hydrocarbon conversion systems is largely a matter of educated guess, empirical evaluation, and a comprehensive understanding of empirical results. The necessity for this approach to the solution of problems such as improving the activity of a given hydrocarbon conversion system, the selectivity of such systems or their tolerance to what might otherwise be process impurities, derives from the lack of an exact understanding of the nature of those factors which limit activity, selectivity and the like or procedures and compositions which can be employed to correct those problems once identified without detracting from other desired qualities of the original system.

One area of development in which the aforegoing observations are particularly pertinent is that of hydrogenative denitrogenation. These systems involve the reaction of organonitrogen compounds with either elemental hydrogen or hydrogen supplied by a hydrogen donor, in the presence of a catalyst comprising molybdenum, at least one Group VIII metal compound and phosphorus supported on a refractory inorganic oxide. Compositions containing these and other elements have been the subject of previous investigation. For example, hydrotreating catalysts comprising a Group VIII metal, particularly cobalt or nickel, a Group VI metal, particularly molybdenum or tungsten, or their oxides or sulfides, and phosphorus on an alumina or silica-stabilized alumina base have been disclosed in U.S. Pats. 3,232,887 and 3,287,280. Those catalysts are discussed as being suitable for denitrogenation or desulfurization of petroleum feedstocks as well as for other hydrogenation reactions. U.S. Pat. 3,287,280, in particular, describes methods and impregnating solutions for preparing such catalysts consisting of molybdenum and nickel salts stabilized with phosphoric acid in an aqueous medium. The author discloses the desirability of maintaining the amount and ratio of the constituents of the impregnating solution within relatively narrow ranges. It is this latter observation that is of particular interest in view of the discoveries I have made in an effort to further understand the functions played by each element of these compositions, the interaction of those functions, and the manner in which those function and interactions are dependent upon the characteristics of a given denitrogenation system. Although the results of these investigations provide some insight into the performance of certain denitrogenation systems, they are not sufliciently comprehensive to afford a general understanding of a significant number of influencing factors.

Nevertheless, I have been able to establish that the ratio of phosphorus-to-Group VI metal employed in such solutions is critical, and that the response of the resulting catalysts in hydrogenative conversion systems is substantially enhanced by the use of higher phosphorus-to-molybdenum metal ratios than are employed in the conventional catalyst preparations. In addition, it has been found that proper regulation of the pH of the solution is essential in order to obtain maximum catalytic activity in these systems.

For the catalysis of hydrogenative hydrocarbon conversions such as denitrogenation or desulfurization, the catalytic metals are generally employed in the form of oxides in association with a carrier material. Conventionally, the catalytic metals are applied to the carrier by impregnation with a solution of a compound of the metal, followed by calcination to convert the catalytic metal compounds to oxides The use of an acid, such as phosphoric acid, is disclosed in the above-mentioned U.S. patents. The disclosed function of the acid is the stabilization of the impregnating solution containing both the Group VI and the Group VIII metal compound.

However, I have found that stabilization of the impregnating solution per se affords a solution for only one of the major problems associated with the impregnation of catalysts with Group VIII and Group VI metal components. It is generally recognized that the formation of an evenly distributed layer of the active components such as the metals, oxides, or sulfides throughout the entire surface area of the catalyst support enables the most efficient utilization of the entire catalyst surface area, i.e., contact surface, and thereby provides the most active catalyst in most applications. The impregnation of such catalyst supports with the active components herein discussed by the use of unstabilized solutions is subject to several distinct disadvantages. For example, precipitation of the active components from solution even prior to contact with the catalyst support occurs to such a significant extent that a considerable amount of the active components are lost as waste material. The catalysts thus formed do not comprise an evenly distributed active component layer. In addition, the active components are deposited on the support surface in the form of crystalline aggregates forming a heterogeneous non-uniform catalytic surface of inferior activity. Precipitation of the active components from the impregnating solution becomes particularly acute at higher concentrations. For this and other reasons hereinafter discussed, it has previously been necessary to employ impregnating solutions of such reduced concentration that multiple impregnations were necessary to deposit the desired amount of active material on the support surface. The multi-step impregnation necessitated by solution instability generally involves the repeated cyclic contact of a support such as silica or alumina with a solution of relatively low concentration. Intermittent partial drying between impregnation cycles is often necessary to render the deposited materials in the form less susceptible to extraction upon contact with additional impregnating medium. This procedure involves a rather involved cyclic batch operation; it is much less attractive than a simpler single step or continuous impregnation-calcination procedure. However, the use of that simplified procedure is not advisable due to the instability of the impregnating solutions. The catalysts thus produced are of inferior activity. This result is believed to be attributable to the distribution of active components on the surface of the support medium in a non-uniform manner as relatively large crystalline aggregates.

The same disadvantages are associated with the use of the so-called stabilized impregnating solutions heretofore employed. The stability of those solutions is not sufficient to enable the use of impregnating media of sufiicient concentration to deposit the desired amount of active components on a catalyst support in a single impregnating step. An even distribution cannot be achieved in a single step due to the fact that impregnating solutions of sutficiently high concentration cannot be maintained in a stable form.

I have also observed that even the catalyst produced by multi-step impregnation with the dilute stabilized solutions of the prior art are markedly inferior to those obtainable by the procedures herein described. The stabilized solutions of the prior art, such as those discussed in U.S. Pats. 3,232,887 and 3,287,280 are more stable in the classical sense than are solutions containing no stabilizing component. Precipitation from these stabilized solutions is less likely in the absence of a support surface, provided the concentration of active components in the impregnating solution is relatively low. However, the active components deposit from these solutions on the support surface as crystallites. This form of deposition is apparently due to the promotion of crystallization of the active components by the support surface. Whatever the cause of crystallite formation, it is understandable that once crystallites form they tend to promote continued crystallization. The result is isolated crystal growth and crystalline aggregate formation in the pores and on the surface. The obvious consequence of this sequence of events is the formation of an unevenly distributed layer of active components on the surface of the support matrix. Such heterogeneity of the catalyst surface is believed to be accountable for the lower activity observed.

The problems observed in the impregnation step are not the only factors involved in forming an active catalyst. The formation of a homogeneous catalyst surface alone does not solve all the problems involved in the preparation of these catalysts. On the contrary, I have observed that the manner in which the catalyst is treated subsequent to impregnation has a dramatic influence on the activity of the finished product. It has previously been considered most expeditions to expose the impregnated support to a preheated furnace in which volatile materials, e.g., Water, are rapidly expelled. However, I have discovered that drying of the impregnated support should be conducted at a rate much less than the maximum in order to obtain the most active product. Although the reasons for this result are not known with certainty, it is presumed that either rapid crystallization or steaming of that catalyst is at least partially accountable. It may be that accelerated drying and the corresponding rapid increase in the solution concentration on the surface promote the formation of crystallites and crystalline aggregates.

It is therefore one object of this invention to provide a hydrogenative denitrogenation system of increased activity. It is another object of this invention to provide an improved method for denitrogenating hydrocarbons. Yet another object of this invention is the provision of an improved system for hydrogenating carbon to nitrogen bonds.

DETAILED DESCRIPTION According to the present invention, it has been found that the use of amounts of phosphoric acid, particularly relative to that of Group VI metal, greater than those taught by the prior art is not only effective in stabilizing the impregnating solution but also substantially enhances the catalytic activity of the finished catalyst. The reason for the enhanced activity of the catalysts of the invention is not known with certainty but is believed to relate to the fact that during the preparation of the catalysts of the invention an amorphous colloidal film of the impregnating materials is deposited on the surface of the support, whereas, in the prior art methods the impregnating materials are deposited in crystalline form. This is believed to result in more uniform distribution of the molybdenum and nickel ions on the surface of the carrier throughout its pore structure when the process of the invention is employed. It can, in fact, be shown that impregnating solutions prepared according to the process of the invention do not crystallize or precipitate upon standing for months at room temperature. Moreover, no crystallized or precipitated material is formed upon drying the solutions in an evaporating dish or in a thin film on glass, metal or ceramic surfaces; instead, a transparent colloidal film is formed. Solutions outside the limits of concentration and pH of the invention crystallize or precipitate before or during drying and yield opaque films on surfaces. The effectiveness of these procedures is demonstrated by the illustrative examples.

As previously mentioned, the conditions necessary to produce an amorphous as opposed to crystalline deposit, at the relatively high concentrations necessary to produce a catalyst of the desired composition in a single step are quite critical. It is presently felt that the most critical of these process conditions are the pH of the solution and the P/MoO weight ratio. The pH necessary to achieve this result in these systems when the molybdenum content exceeds about 17 weight-percent of M00 must be within the range of 1 to about 2 for the solution initially contacted with the substrate. I have observed that pH values slightly above 2, i.e., up to about 2.5, can be employed without intolerable activity losses at somewhat lower M concentrations such as those that exist during the latter stages of impregnation when the concentration of active components is substantially diminished due to the deposition of those components on the catalyst support. However, the pH should be maintained as close as possible to about 1.5 i.e., about 1.2 to about 1.8. Deviations from that midpoint in either direction render the impregnating solution less stable, particularly at M00 levels of about 17 percent and above. The greater the deviation, the greater the prospect of crystalline deposit formation and crystallite aggregation on the support surface.

In accordance with another embodiment of this invention organonitrogen compounds are denitrogenated upon contacting with the described catalyst under a superatmospheric hydrogen partial pressure and conditions of temperature, pressure and contact time sufficient to denitrogenate at least a substantial proportion of the organonitrogen compounds.

In accordance with another embodiment hydrocarbon feeds containing organonitrogen by contacting in a reaction system including the hydrocarbon feed, the described catalyst and denitrogenation conditions including a superatmospheric hydrogen partial pressure.

The required amount of phosphorus is most conveniently expressed as the ratio of the weight of elemental phosphorus to the weight of the Group VI metal oxide. For example, in the specific examples below, the amount of phosphorus is expressed in terms of the phosphorous-tomolybdenum oxide weight ratio, i.e., P/MoO It has now been found that this ratio should be at least about 0.1 in order to achieve the desired improvement in the catalytic activity. On the other hand, the use of too high a concentration of phosphorus generally results in diminished catalytic activity. Consequently, the P/MoO ratio in the product should be within the range of 0.1 to about 0.25, preferably from 0.12 to about 0.23.

Catalysts having these compositions are conveniently prepared by multi-step impregnations, e.g., circulation dip, with solutions having P/MoO ratios corresponding to those desired in the calcined product. The solutions generally contain from 10 to 30, usually 17 to 30, weightpercent M00 about 1 to 10 weight-percent of the selected Group VIII metal oxide and 1 to about 6 weightpercent phosphorus on an equivalent basis. However, when the simpler, more efiicient single step pore saturation method is employed the solution should contain the equivalent of about 17 to about 30, preferably 17 to about 24, weight-percent M00 1 to about 8, usually 1 to 5 Weight-percent of the Group VIII metal oxide and 2 to about 6 weight-percent phosphorus.

When impregnation is accomplished by prolonged immersion of the foraminous base with excess solution, somewhat lower molybdenum concentrations can be employed. For example, the equivalent oxide mole ratios can be within the range of 10 to 17 weight-percent M00 2 to 10 weight-percent of the Group VIII metal oxide and 1 to 4 weight-percent equivalent elemental phosphorus. In these systems the P/MoO ratio is preferably somewhat lower than in the pore saturation techniques since phosphorus is deposited at a faster rate than is the molybdenum or Group VIII component. Higher pH, e.g., up to about 2.5 can also be tolerated in the more dilute solutions. However, it is still preferable to assure that the initial pH of even these dilute solutions is within the range of 1 to about 2.

Group VIII metals, suitable for use in the invention are iron, cobalt and nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The most attractive Group VIII and Group VI metals in these systems are cobalt, nickel, molybdenum and tungsten. However, these methods exhibit the most significant superiority when employed to prepare catalysts of molybdenum and a Group VHI metal, particularly nickel or cobalt, due to the relative instability of molybdenum-containing solutions.

Optimum proportions of the molybdenum and the Group VIII metals in the finished catalyst will vary over a considerable range, again depending on the particular metals, the reaction in which the catalyst is employed, the carrier, etc. Optimum proportions are best determined experimentally and can readily be ascertained by one of ordinary skill in the art. Generally the Group VIII metal, based on the oxide, will comprise about 1 to 10, preferably 1 to 6 weight-percent of the catalyst, with the M00 comprising about 5 to 40, preferably 10 to 20 weight-percent of the catalyst.

The required phosphorus-to-Group VI metal oxide in the finished catalyst is obtained by employing suitable concentrations of the phosphorus acid and the Group VI metal compound in the impregnating solution. Suitable concentrations will, of course, vary considerably with the particular Group VI and Group VIII metal compounds, the phosphorus acid, the carrier, the pH and temperature of the impregnating solution, method of effecting the impregnation, etc., and are best determined empirically. For example, the most preferred acid of phosphorus concentration will not generally be exactly the same in systems employing different forms of molybdenum or nickel.

Orthophosphoric acid is the preferred source of the phosphorus component of the catalyst of the invention. However, other phosphorus acids such as metaphosphoric acid, pyrophosph'oric acid, phosphorus acid, etc., may be used. The compound of the Group VI metal, preferably molybdenum, can be any one or a combination of a variety of substances which have sufiicient solubility in the solution to enable the deposition of the desired amount of metal. Illustrative compounds are the acids, oxides, and the simple and complex salts such as molybdenum trioxide, molybdenum blue, molybdic acid, ammonium dimolybdate, ammonium phosphomolybdate, ammonium heptamolybdate, nickel and cobalt containing molybdates and phosphomolybdates and the like. Molybdenum is presently preferred since the resultant components are the more active conventional components.

The presently preferred Group VIII metal sources are the salts of strong acid anions. Exemplary of such anions are nitrate, sulfate and the halides, particularly bromide, chloride and fluoride anions. The preference is due primarily to the fact that the strong acid anions dissociate on admixture with the acid of phosphorus and the molybdenum source to form the corresponding acid. The strong acids are necessary to reduce the pH to a point within the essential range, i.e., 1 to about 2, at the preferred concentration levels of the respective metal sources. The nitrates are presently the preferred source of the Group VIII metal, nickel nitrate being particularly preferred due to the high activity of the resultant catalyst. Ammonium heptamolybdate is the presently preferred molybdenum source due to its high solubility. The anions other than nitrates are generally less preferred due to significant difficulties associated with their use. For example, the halides, derived from the Group VIII metal halide source, are useful in preparing these compositions but result in the evolution of the acidic halide or hydrogen halide gas upon drying and/or calcination. These materials are highly corrosive and are preferably avoided. The sulfate, on the other hand, is somewhat more difficult to keep in the original solution, making it advisable to employ slightly elevated temperatures, i.e., from to about F., depending on the concentrations of the Group VIII metal sulfate. However, the use of the sulfate salt does have a distinct advantage. In the preparation of sulfided catalyst the conditions of calcination can be controlled so that the sulfate is not completely driven off and can be chemically reduced to produce a sulfided composite having a much more homogeneous distribution of sulfur than could otherwise be achieved. For example, the sulfate reduction can be conveniently carried out by exposing the calcined catalyst to a reducing atmosphere of hydrogen, carbon monoxide, etc.

A portion of the Group VIII metals can also be added in the form of salts of weak acids or as the hydroxides when it is desirable to raise the pH of the impregnating solution by this procedure. For example, if the admixture of the desired amounts of the active metal salts and acid of phosphorus results in a formation of a solution having a pH somewhat lower than desired in a particular application, the pH can be raised by the addition of a Group VIII metal base such as nickel or cobalt hydroxides and carbonates. However, this procedure is not presently preferred in that it requires the commensurate correlation of pH and active metal concentrations. As a result it is presently more preferred to raise the pH When it is initially lower than desired by the addition of a base not having a metal cation, such as ammonia. In any event, where base addition is employed to modify the initial pH, the amount of added base should not be so great as to increase the pH to a value outside the prescribed range.

Several procedural steps can be employed in the impregnation of the catalyst substrate with the compositions referred to. One such method, entitled the spray technique, involves spraying the support with a solution of the desired composition. The single-dip or pore volume method involves dipping the support in the solution for a period sufficient to fill the pores with impregnating medium. The application of vacuum is generally preferred in the latter approach. The impregnating solution can more readily displace air trapped in the interior pore volume of the catalyst support at reduced pressures.

The amount of active components retained on the support will depend largely on the pore volume and adsorption capability of the support. Consequently, the charac teristics of the support must be taken into account in determining the conditions necessary to obtain a composite of predetermined composition. In general, the preferred supports, e.g., alumina and silica-stabilized alumina, will have pore volumes of 0.6 to about 1.4 cc./ gram and adsorption capacity sufficient to retain the desired amount of solution in a single step. Some variation in pore size outside this range will be encountered with other supports within the general class of inorganic refractory oxides, e.g., combinations of silica and alumina such as natural and synthetic crystalline and amorphous aluminosilicates and gels such as silica-alumina and silica-magnesia, to which this invention is applicable. Pore size should also be taken into account in designing the most appropriate systems for the impregnation of a given support. As a general rule more care should be taken in the preparation of relatively large pore size catalysts. Better deposit homogeneity and higher activity are obtained by using longer aging times prior to drying and more gradual drying procedures. These observations are particularly applicable to the impregnation of acid leached supports in which a portion of the pores are usually fairly large.

Following either of these procedures the impregnated support can be dried and calcined to produce a catalyst having the desired active mtal concentrations, provided the concentration of the active metals in the solutions is sufficient to deposit the desired amount of active metal compound on the support in a single step. This is one significant advantage of these novel solutions. The stability of solutions of much higher active component concentration can be maintained for considerable periods even in the presence of inorganic supports. When a single step approach is employed it is, of course, necessary to incorporate a definite amount of each active constituent into the impregnating medium and maintain the proper ratios between the several constituents per unit volume of solution in order to obtain a finished catalyst of the desired composition. It is also preferable to age the impregnated particles for at least about 30 minutes and preferably up to about 8 hours before drying and calcining. Aging after pore saturation, in the absence of excess solution, under mild conditions, i.e., 70 F., to about 150 F. results in more even distribution of active components and improved activity.

Additional precaution should be taken when a support material containing aluminum ions is exposed to excess solution at relatively low pH. It is believed that certain constituents of the impregnating solution, particularly the acid of phosphorus, react with aluminum and degrade the support, foul the impregnating solution and result in the formation of undesirable chemical forms on the finished catalyst. As a result, the duration of contacting, particularly with alumina-containing supports should not be excessive.

Another impregnating method which has found wide application due to the previous necessity for maintaining relatively low active component concentrations is the cyclic or multi-dip-procedure wherein the active support is repeatedly contacted with impregnating solution with or without intermittent drying. As previously mentioned, this procedure is less desirable in that it necessitates the use of procedures far more complicated than the single-dip or spray technique. Yet another procedure employed by the prior art, which is not necessary with these impregnating solutions involves a prolonged contacting step at slightly elevated temperatures, e.g., 100 to 150 F., to promote the incorporation of active components onto the support.

In the circulation dip impregnation procedure the impregnating solution may be circulated through a bed or catalyst support particles until the required amount of the active constituents are deposited. A more dilute solution having a higher equivalent P/MoO ratio and somewhat higher pH may be employed when using this technique and the active component concentration in the circulating solution can be replenished as necessary during the impregation cycle in order to build up the desired concentration of active components on the support. Equivalent P/MoO ratios as low as 0.5 and pH as high as 2.5 may be employed in this process, provided the total concentration of active constituents is reduced by a factor of at least 40% so that the equivalent Group VI and Group VIII oxide concentrations do not exceed 14 and 4 weight-percent, respectively. These reduced concentrations are necessitated by the greatly reduced stability of the impregnating solution due to the higher pH and lower P/MoO ratios.

The exact concentration of the various constituents in the solution must be determined with regard to the final catalyst composition desired, the pore volume of the support particles and the time of contact of the support particles and the stability of the impregnating solution. A wide range of active component concentrations can be employed although some limitations are imposed by the selected impregnation procedure. Representative concentrations are 10 to 30 weight-percent M00 and 1 to 10 weightpercent of the Group VIII oxides. The solutions employed in the pore saturation technique are necessarily relatively concentrated. Active component concentrations in those systems should be somewhat higher, correspoding to 17 to about 30 weight-percent M00 and 2 to about 8 weightpercent of the Group VIII metal oxide, and must be determined in relation to the desired composition of the final product. Nevertheless, the relative ratio of the Group VIII component to the Group VI component will generally be higher in these dilute systems when an excess of impregnating medium is employed. This is particularly true in the case of molybdenum, tungsten, nickel and cobalt. It has been observed that the Group VI component combines with the substrate more rapidly than does the Group VIII component. Consequently when deposition of the active components onto the substrate is effected at least in part by adsorption as in the single dip and circulation dip techniquesthe Group VIII to Group VI component ratio required to obtain a given final composition is higher than that required in the absence of selective 9 adsorption effects. In contrast, the final Group VIII to Group VI component ratio is determined directly by solution composition when the pore saturation or spray techniques are employed. Selective adsorption effects are not determinative in these systems.

The pH of the solution will generally vary somewhat upon the addition of the Group VIII metal salt. The degree of such variation depends primarily upon the strength of the salt anion. For example, the addition of nickelous nitrate reduces the pH of the solution somewhat. The degree of this pH reduction is greater than that experienced when sulfate salts are employed due to the fact that the nitrate is the anion of a stronger acid than sulfuric acid. As a consequence of this effect, it is generally desirable to further adjust the final pH of the solution after addition of the Group VIII metal salt to the preferred value of from 1 to about 2, preferably from about 1.3 to about 1.7. If the pH of the final solution is lower than about 1 and higher than about 2, the stability of the final solution is reduced with the consequent appearance of precipitates or crystallites in the more concentrated solutions.

The desired stability of the impregnating solution is easily demonstrated by spreading a thin layer of the solution on a glass slide and allowing it to dry gradually under ambient conditions. The stable solutions prepared by the procedure herein described will dry to a completely amorphous transparent film as demonstrated by X-ray diffraction examination of the resultant film. Solutions not meeting these criteria do not form transparent thin films under conditions of this test but become opaque or translucent on drying due to precipitation and/or crystallization.

As illustrated by the examples hereinafter discussed, the catalysts prepared from the less stable impregnating solutions are far less active than those prepared from the solutions herein described. It appears that these differences in activity are attributable, at least in part, to the formation of crystallites and precipitates during impregnation. It is believed that this precipitation and crystallite formation results in the segregation of the several constituents into different crystalline species and the consequent formation of heterogeneous active component deposits. This type of segregation is prevented by the use of the impregnation solutions of this invention.

I-Iydrogenative denitrogenation systems are very well known in the hydrocarbon processing and chemical industries. Although a number of reactions may occur in such systems depending upon the nature of the feedstock and the severity of operating conditions, the methods are characterized by the conduct of a substantial amount of reaction between hydrogen and organonitrogen compounds. This reaction is generally considered to involve hydrogenation of the carbon-to-nitrogen bonds in such compounds. However, any reaction which serves to remove nitrogen from the organonitrogen compounds originally in the feed is effective for the desired objective, i.e., denitrogenation.

The methods of this invention can be employed to denitrogenate essentially any nitrogen containing hydrocarbon base feedstock. Hydrocarbon feeds usually employed in such operations boil primarily above about 100 F., generally above about 400 F. The most common denitrogenation systems employ hydrocarbon feeds boiling within the range of about 400 to about 1300 F. These conversions are usually effected by contacting the feed with a fixed bed catalyst system as opposed to fluidized or dispersed phase catalyst systems. However, in dealing with very high boiling feedstocks, i.e., in excess of about 1200 F., it becomes desirable, due to the consistency of the feed, to disperse the catalyst in the form of fine particles in the hydrocarbon phase and carry out the desired degree of denitrogenation in the liquid phase followed by separation of the catalyst from the hydrocarbon.

Nitrogen concentrations also vary considerably and are usually in excess of about 2 parts per million nitrogen present as organonitrogen compounds. However, most feedstocks have considerably higher nitrogen levels, i.e.,

in excess of about 10 parts per million usually in excess of about 50 parts per million. The great majority of hydrocarbon feeds, however, that are subjected to denitrogenation contain amounts of organonitrogen compounds equivalent to about 10 parts per million to about 1% nitrogen.

The reaction conditions necessary to effect the desired degree of denitrogenation can be readily determined by one skilled in the art for a particular feedstock and design conversion per pass. For example, the selected feed can be contacted with the described catalyst at a set of test conditions and the degree of conversion determined by product analysis. The severity of the process can then be increased or decreased as desired by increasing reaction temperature, hydrogen partial pressure, total pressure and/ or contact time. However, as a general rule, reaction temperatures will be in excess of about 400 F., usually within the range of 400 to about 950 F. Total reaction pressures are generally in excess of 500 p.s.i.g., usually about 500 to about 5000 p.s.i.g. Superatmospheric hydrogen partial pressures are always employed. In conventional terms the hydrogen concentrations are usually equivalent to at least about 50 standard cubic feet per barrel, generally in excess of 100 and usually about 400 to about 20,000 standard cubic feet per barrel. These hydrogen concentrations generally correspond to hydrogen partial pressures of at least about 50 p.s.i., often about 100 to about 3000 p.s.i. The hydrofining conditions presently preferred for most feedstocks include temperatures of about 700 to about 800 F. and hydrogen partial pressures of about 750 to about 2000 p.s.i.

Some denitrogenation can of course be effected With relatively short reaction times. However, the accomplishment of substantial conversion usually requires contact times in excess of 1 minute, preferably in excess of about 5 minutes. In that most denitrogenation systems are conducted in the presence of fixed bed catalysts, contact times are more conveniently expressed in terms of liquid hourly space velocities (LHSV) which are always in excess of about 0.1, usually at least about 0.4 and generally within the range of 0.4 to about 15.

The selected operating conditions should be sufficient to reduce the organonitrogen content by at least about 50%. Conversions in excess of about are often preferred. However, in most instances, it is preferable to reduce the final organonitrogen content to a level below about 10 parts per million.

As previously mentioned, it is sometimes the case and in fact it is sometimes desirable that other reactions occur along with denitrogenation upon exposure of the described feedstocks to the methods of this invention. However, when denitrogenation is the primary objective it may be desirable to minimize the extent of one or more other reactions such as hydrocracking. For example, it is often desirable to effect the desired degree of denitrogenation while affecting less than 20% conversion of the feed to hydrocarbons product boiling below the initial feed boiling point. Several of the by-products of hydrofining processes such as ammonia will of course boilbelow the initial boiling point of the hydrocarbon feeds. These materials however are not intended to be included in the specification of hydrocarbon conversion. A similar criteria which can be employed to specify the presence or absence hydrocracking regards to the number of moles of hydrocarbon product recovered as compared to the number of moles of hydrocarbon feed. Lighter by-products such as ammonia produced as the natural consequence of denitrogenation are of course not included in these molar values. For the purposes of these methods and to a large extent throughout the hydrocarbon refining technology, it is considered a process that produces less than 110 moles of hydrocarbon product for every holes of hydrocarbon feed does not involve substantial hydrocracking. Consequently, the methods of this invention can be controlled to produce less than 20% hydrocarbon product boiling below the initial feed boiling point or less than 110 moles of hydrocarbon product for each 100 moles of hydrocarbon feed when it is desirable to conduct the described denitrogenation in the absence of substantial hydrocracking.

The following examples serve to more particularly illustrate the invention and the advantages thereof.

Examples 1-7 B Feed a B Feed Log B Product B Product (from X (from Ref. Cat.) Cat.)

X 100 Activity Percent denitrogenation was also calculated from the total nitrogen in the product averaged over the last 12 hours on the feed. Results are given in Table I in which the denitrogenation (DeN) activities are expressed as volume percent and weight percent relative to the activity of the reference catalyst. The latter is a commercial hydrotreating catalyst consisting of 16.4% M 2.9% NiO, and 1.3% P on gamma alumina stabilized with 4.5 weight percent silica. This catalyst was prepared by impregnating the support with an aqueous system containing 17.4 wt. percent M00 as ammonium heptamolybdate and 3.5 wt. percent NiO as nickel nitrate with a P/MoO weight ratio of 0.085 at a pH greater than 2.6.

TABLE I COMPOSITIONS AND DENI'IROGENATION ACTIVITIES OF CATALYSTS OF EXAMPLES Reference Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 catalyst Solution composition wt. percent:

Catalyst composition wt. percent:

M003 15. 2 21. 7 18. 4 18.2 10. 5 18. 4 16. 9 16. 3 NiO 2. 3.07 2. 07 2. 96 2.88 2. 03 2. 82 2. 8 P 2. 81 2. -10 2. 96 3. 04 3. 41 3. 26 3. 58 1. 30 P/MoO; 0. 185 0. 0.162 0. 166 0.175 0. 175 0.210 0. 050 Activity weight of catalyst, g 164 175 171 171 175 151 167 146 Vol. percent of DeN activity. 140 123 150 154 137 1 10 1 13 100 Wt. percent of DeN activity- 12 10 2 132 116 127 100 Percent DeN 96. 21 96. 56 96. 67 91. 8

ticles were contacted for the designated period under 22 mm. vacuum and decanted on a #5 Biichner funnel. The catalysts were then dried and activated by heating at a rate of 50 F./hr. up to 900 F. at which they were maintained for 2 hours. Each of the catalysts was activated by the preferred calcination procedure by intimately contacting the impregnated pellets with 6 to 8 s.c.f. of ambient air at about 70 F. inlet temperature per pound of catalyst per minute throughout the period of drying and calcination.

The calcination was carried out in a muffie furnace fitted with a fine screen rack on which the specimen was spread in a thin layer, no deeper than about /2", through which air was passed during drying and calcining. About 500 to 1000 grams of wet impregnated catalyst particles were placed on a stainless steel screen 15 x 15" square having less than 10 mesh per inch. This screen is supported on a perforated stainless steel tray positioned on a furnace rack in an electrically heated vertical draft oven having an air inlet at the base. Air was blown into the bottom of the furnace at a rate of 4 to 12 standard cubic feet per minute and passed up through the furnace and through the bed of catalyst supported on the porous screen.

The hydrofining activity of each catalyst was determined by passing a mixed gas oil over a fixed bed of catalyst at a temperature of 725 F., a pressure of 1400 p.s.i.g., space velocity of 2.0 LHSV and a hydrogen rate of 6000 s.c.f./barrel of feed. The mixed gas oil feed had a boiling point range of 400 to 900 F., and API gravity of 23.2 and contained 1.19 weight percent sulfur and 0.195 weight percent nitrogen. The residual basic nitrogen in the liquid product, after scrubbing with 5% sodium hydroxide, was monitored and used to calculate percent activity with reference to a standard catalyst by the following equation:

The volume percent activity of the catalyst of Example 1, in which the P/MoO ratio was 0.185 and the initial pH of the impregnating solution was 1.9, was of the reference catalyst. The catalyst of Example 2, in which the P/MoO weight ratio in the product was only 0.11 and the initial pH of the impregnating medium was 2.0, had an activity of only 123 volume percent of the reference catalyst. This difference was even more pronounced on a weight basis of conversion, i.e., 123 versus 103. The catalyst of Example 1 was the most active even though it contained less active metal. The catalyst of Example 3 prepared at an initial solution pH of 1.3 and a P/MoO solution ratio of 0.136 exhibited even higher activity. Example 4, similar to Example 1 in M00 content, P/MoO ratio and solution pH but employing a different carrier, had an activity similar to Example 1. Example 5, in which the equivalent NiO content was somewhat lower and the initial solution pH was 1.3 had lower activity than Example 4, but was still considerably more active than the low P/MoO ratio catalyst of Example 2. Examples 6 and 7 impregnated at pH of 1.9 and 1.3 respectively, show that a further increase in the P/MoO ratios to 0.175 and 0.21, respectively, does not result in any further increase in activity. In fact, the activities of these examples were less than that of Examples 3 and 4. The markedly higher activity of the catalysts prepared from impregnating solutions having pH values, P/MoO ratios and active component concentrations Within the prescribed limits is readily apparent by comparison with the reference catalyst produced under conditions preferred by the prior art.

Examples 8-21 These investigations were conducted to evaluate the effect of impregnating solution composition on the stabil- 13 ity of the amorphous deposits formed in accordance with the method of this invention. Each of these solutions was prepared by dissolving ammonium heptamolybdate and phosphoric acid (85%) in water in the proportions reported in Table 2. The indicated amount of nickelous l4 addition of suflicient ammonium hydroxide to increase the pH from the original value of 1.25 to the final value of 1.60. It is believed that the presence of ammonium hydroxide in solutions having P/MoO ratios approaching the lower prescribed limit of about 0.1, i.e., 0.136

nitrate hexahydrate was then added to the solution. In 1n Example 12, tends to reduce the stability of those several instances the pH of the final solution was adjusted solutions. This conclusion is borne out by Example 14 upwardly by the addition of ammonium hydroxide in in which suflicient ammonium hydroxide was added to amounts sufficient to produce the indicated pH change. the solution to increase the pH from the original value Each solution was aged overnight (12 hours) at 75 F. of 1.1 to a final pH of 1.60. The P/MoO ratio in that in glass bottles. Equal portions of each fresh solution preparation was 0.176 which was high enough to counterwere also deposited on glass slides and dried gradually act the effect of base addition as indicated by the comat 75 F. Visual observations for both of these tests are plete absence of any opaqueness or precipitate in either reported in Table 2. the dried film or aged solution.

TABLE 2 Example No 3 9 10 11 12 13 14 15 10 17 13 10 20 21 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 25.5 41.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 33.0 20.91 33.0 7.0 10.4 12.0 17.0 17.5 22.0 22.0 27.0 27.0 17.0 22.0 27.0 0.0 None 1.88 2.30 3.23 4.57 4.70 5.01 5. 01 7.20 7.20 4.57 5.91 7. 20 1.77

75 75 75 75 75 75 75 75 75 75 75 75 75 75 pH 4.5 3.5 2.9 1.7 1.75 1.0 1.5 1.4 1.45 1.75 1.45 Nickelous nitrate hexahydrate, g. 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 10.5 24.0 0, 0.10 0.10 0.10 0.10 6.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 4.24 Total volume of solution,m1 120 120 120 120 120 120 120 120 120 110 110 100 120 120 pH 3.5 2.3 1.9 1.3 1.25 1.15 1.1 1.05 1.0 1.3 1.0 26 M Adjust pH with NHlOH. None None None None 1.60 None 1.60 None 1.70 2.3 2.3 2.3 None None 120 120 0 123.5 120 125 120 132 120 121 113 120 120 0.2325 0.2325 0.2325 0.2325 0.230 0.2325 0. 203 0.2325 0. 255 0.2325 0. 2325 0.2325 0.1742 0.2325 0.0517 0.0517 0.0517 0.0517 0.0515 0.0517 0.0512 0.0517 0.047 0.0517 0. 0517 0. 0517 0. 0353 0.0517 0.0157 0.0233 0.0200 0.0334 0.0330 0.0493 0.0472 0.0005 0.055 0.0330 0. 0472 0.0005 0.0143 0.050 0.033 0.095 0.130 0.130 0.170 0.170 0.210 0.210 0.130 0.170 0. 210 0.035 000 Yellowish opaque (Z) Film cracking Crystalline deposit.

Yellow fine crystalline precipitate (J 1 Transparent.

1 Slightly opaque. 3 Opaque yellow. 4 Clear.

6 Trace sediment.

1 Glass bottles containing the 3 solutions were lined with crystalline material .1111 is too high for stable solution.

' Precipitate with yellow fines formed slowly.

B White precipitate begins to form in 510 min. voluminous after 1 hour.

The impregnating solutions of Examples 8, 9 and 10 were all unstable as indicated by the formation of yellowish opaque precipitates on the glass slides and the formation of yellow fine crystalline deposits in the solutions aged for 12 hours at 75 F. The observed instability is believed to be attributable to the low solution P/MoO weight ratios, all of which are below the minimum of about 0.10 necessary to obtain the advantages of this invention. It is interesting to note, however, that these ratios are equivalent to those considered preferable by the prior art. In addition, the solutions of Examples 8 and 9 had pH values of 3.5 and 2.3, respectively, both of which exceed the maximum pH of 2.0 tolerable in these relatively concentrated solutions. The precipitate formation observed in Example 10 at a pH of 1.9 and P/MoO weight ratio of 0.095 was much slower than that observed in either Example 8 or 9, although the dried film definitely exhibited an opaqueness characteristic of a heterogeneous or crystalline system. The presence of precipitate in the aged solution was apparent after 12 hours. Although the degree of instability was reduced by reducing the pH to 1.9 in Example 10, the P/MoO weight ratio was so far below the necessary minimum of about 0.1 that some instability was apparent in the dried film and aged solution.

Examples 11 through 14 were conducted at conditions of pH and P/MoO ratio within the limits prescribed by this discovery and illustrated remarkable stability in both the dried films and aged solutions. A trace amount of precipitate was observed in the solution of Example 12 after 12 hours of aging at 75 F. However there was no concurrent opaqueness in the dried film and the aged solution was evidently far more stable than the solutions of Examples 8-10. The presence of the trace precipitate in the aged solution of Example 12 is attributed to the Comparison of Examples 15 and 16 provides a dramatic illustration of the advantage obtained by increasing solution pH with basic media. The solution of Example 15 having a pH approaching the minimum prescribed limit and a P/MoO weight ratio approaching the upper limit prescribed for that parameter was somewhat less stable than the solutions of Examples 11-14. The dried film exhibited a slightly opaque appearance and trace amounts of solid sediment were present in the aged solution. Although solutions of this nature are less preferred, they are still far superior to the solutions envisioned by the prior art and illustrated by Example 20. That solution, having a pH of 2.6 and a P/MoO ratio of 0.085 produced an opaque yellow heterogeneous deposit on the glass slide. The formation of fine yellow particulate matter was evident in the aqueous solution throughout the aging period. The significance of the poor stability of that solution is even more apparent when it is observed that the total metals concentration in Example 20 was about 85% less than the stable solution of this invention. Obviously the tendency toward precipitation is greater at higher concentrations. Yet the solutions of this invention remained stable at concentrations about higher than those at which substantial instability was observed in Example 20.

It should also be observed that the value of this distinction becomes even more apparent in the context of catalyst preparation systems. The savings in time and investment alone afforded by single-step impregnation techniques are readily apparent. Yet the application of such techniques requires the use of impregnating solutions of relatively high concentrations to enable the deposition of the desired amounts of active components. The markedly superior compositions of this invention enable the use of those systems to produce catalysts of superior activity.

The composition of Example 16 having a P/MoO weight ratio identical to Example 15 and an intial pH of 1.0 was further treated by the addition of sufficient ammonium hydroxide to increase the pH to 1.70. The resultant solution was very stable and produced a completely transparent dried film. The aqueous solution remained completely clear even after aging for 12 hours.

The effect of higher pH on the stability of impregnating solutions having active component concentrations suflicient to enable the use of single-step impregnating methods is illustrated by Examples 17-19. Several P/MoO ratios were investigated in these examples. All three of these solutions having pH values of 2.3 and P/MoO ratios representative of the prescribed range were much less stable than the solutions of Examples 11-16. The formation of opaque cracked films and substantial crystallization in the aged solutions were observed in each instance.

The solution of Example 21 provides a contrast between the stable solutions having pH values and P/MoO ratios within the necessary limits to similar prior art solutions prepared at higher pH in the absence of an acid or phosphorus.

Examples 22 and 23 These two examples illustrate the influence of aging the substrate in contact with impregnating medium on the activity of the resultant catalyst.

A solution containing 410 grams of ammonium heptamolybdate, 210 grams of 85% orthophosphoric acid and 220 grams of nickelous nitrate hexahydrate made up to a total volume of 950 ml., and pH adjusted to 1.3 by the addition of several ml. of concentrated ammonium hydroxide was dripped from a separatory funnel onto 1300 grams of silica-stabilized alumina extrudates in an evacuated 4-liter flask. The flask was vigorously shaken by hand during and after the addition of the solution to aid in its distribution. This volume of solution was enough to -fill the pore volume of the extrudates and wet them enough so that they adhered to each other and the flask. There was no free liquid in the flask. The agitation under vacuum was continued for minutes. The temperature of the wet extrudates increased from about 77 F. to about 122 F. during this period of time. The wetted and impregnated extrudates were divided into two parts.

A 1000 gram portion of the impregnated extrudates which had been aged for 20 minutes was spread on a stainless steel screen tray in the Kress box muffle furnace and dried at 200 F. for 16 hours. The dried pellets were then distributed on a stainless steel screen suspended within a top-opening Kress muffie furnace and heated at a controlled rate of 50 F. per hour to 900 F., at which temperature they were maintained for two additional hours. Throughout the entire drying and calcination period ambient air, having an inlet temperature of 75 F. was passed into the bottom of the furnace and over the yellets at a rate of about 7 standard cubic feet per minute per pound of catalyst.

The remaining material in the 4-liter impregnating flask was aged under ambient conditions with occasional shaking by hand for an additional 100 minutes. The impregnated and aged extrudates were then distributed on a 15 square stainless steel tray and placed in an oven at ambient conditions. The oven was turned on and heated to 200 F. and the catalyst was held at that temperature for 16 hours. House vacuum was applied to draw air through the oven during this period. The dried extrudates were then calcined in the Kress box-type muflle as described above. The composition and activity of these two catalysts were determined as in Example 3 and are compared in Table 3.

TABLE 3 Composition, wt. percent Activity test Aging Example time, I Percent No. minutes M00 N10 P Hours activity These results demonstrate that considerable advantage can be achieved by aging catalysts impregnated by single step pore saturation.

The following four examples demonstrate the superiority of the methods of this invention. All of these examples were conducted on the feedstock having the properties illustrated in Table 4.

TABLE 4.FEED PROPERTIES Excludes 9.9% of total aromatics present as sulfur compounds and reported as such.

Example 24 The catalyst of this example was similar to the reference catalyst discussed in Table I and was prepared by impregnation of an alumina support stabilized with 5 weight-percent silica. The impregnating medium comprised an aqueous solution of ammonium heptamolybdate, nickelous nitrate hexahydrate and orthophosphoric acid in amounts corresponding to about 17.4 weight-percent M00 about 3.5 weight-percent NiO, and about 1.5 weight-percent P. The previously described pore saturation technique was employed to effect this impregnation. The impregnated composite was then dried and calcined at a maximum temperature of about 900 to about 950 F. in the absence of substantial circulating air flow through the calciner. The resultant activated composite had a composition corresponding to 15.6 weight-percent M00 3.2 weight-percent NiO, and about 1.3 weight-percent P.

This catalyst was then used to convert the feed identified in Table 4 in a fixed bed catalyst system operating once through with a single stage at 740 F., 1275 p.s.i.g., a liquid hourly space velocity (LHSV) of 0.59 and a hydrogen injection rate of 6000 standard cubic feet per barrel of hydrocarbon feed. The results of this operation are summarized in Table 5.

Example 25 The hydrogenative conversion of Example 24 was repeated using the catalyst described in Example 24 and the feedstock identified in Table 4 at a reduced temperature of 715 F. to provide a comparison between these methods at somewhat less severe conditions. The results of this operation are also summarized in Table 5.

Example 26 The method demonstrated in this example employed a catalyst prepared by the circulation dip method using a solution containing 13.4 weight-percent M00 about 3.6 weight-percent NiO, about 1.2-1.3 weight-percent P and having an initial pH of about 2.5 and a P/MoO ratio of about 0.11. The finished catalyst had an equivalent composition of 16.6 weight-percent M 3.27 weight-percent NiO, and 3.09 weight-percent P on gamma alumina stabilized with 4.5 weight-percent silica. This catalyst was used to convert the feed identified in Table 4 in a single-stage once through system using hydrogen at conditions otherwise identical to those described in Example 24. The results of this operation are summarized in Table 5.

Example '27 The hydrogenative conversion described in Example 26 was repeated at conditions of less severity at a temperature of 715 F. to provide a comparison to the method demonstrated in Example 25. The results of this operation are summarized in Table 5 along with the results of These examples again confirm the dramatic superiority of the methods of this invention for denitrogenation as compared to what might heretofore have appeared as analogous processes. At otherwise identical conditions the methods of this invention were elfective in reducing the final organonitrogen content of the product to 0.9 and 1.2 parts per million equivalent nitrogen in Examples 26 and 27, respectively. This performance is contrasted to the total product nitrogen concentrations of 19 and 35 parts per million, respectively, for the comparison methods of Examples 24 and 25 These results speak for themselves. As in all conversion systems other than zero order reaction rate is a function of remaining reactant concentration with the consequence that reaction rate diminishes as the concentration of reactants are reduced. In the case at hand the reactant being monitored is the organonitrogen content of the feed. The concentration of that constituent was reduced to a point at least about 20 times below the final nitrogen concentration in the comparative methods. This arithmetic difference would have been even greater had the reaction been terminated earlier at higher remaining nitrogen concentrations in both systems. In either event the superiority of the denitrogenation methods of this invention is readily apparent. Numerous variations and modifications of the concept of this invention will be apparent to one skilled in the art in view of the aforegoing disclosure and the appended claims.

What is claimed is:

1. The method of hydrogenatively denitrogenating a hydrocarbon feed containing at least p.p.m. nitrogen as organonitrogen compounds which comprises reacting said feed with hydrogen under a superatmospheric hydrogen partial pressure and denitrogenation conditions of temperature, pressure and contact time sutficient to reduce the organonitrogen content of said feed with the catalytic composition formed on impregnating a foraminous refractory oxide with an aqueous impregnating medium having an initial pH below about 2 which forms on the admixture of a molybdenum compound selected from ammonium heptamolybdate, ammonium phosphomolybdate, molybdic acid, molybdenum trioxide and molybdenum blue, a water soluble compound of nickel or cobalt and an acid of phosphorus, in proportions equivalent to about 10 to about 30 weight-percent molybdenum trioxide and about 1 to about 10 weight-percent of nickel or cobalt oxides at a P/MoO ratio of about 0.1 to about 0.25.

2. The method of claim 1 wherein said Group VIII metal salt is selected from the nitrates, sulfates, fluorides, chlorides and bromides of nickel and cobalt, said molyb- 18 denum compound is ammonium heptamolybdate, said acid of phosphorus is orthophosphoric acid, and the initial pH of said medium is Within the range of about 1 to about 2.

3. The method of claim 1 wherein said catalytic composition comprises an equivalent M00 content of about 5 to about 40 Weight-percent and about 1 to about 10 weight-percent of nickel or cobalt oxides.

4. The method of claim 1 wherein said hydrocarbon feed boils primarily above about F. and contains at least about 50 parts per million nitrogen as organonitrogen compounds, said water soluble compound is present in an amount equivalent to about 1 to about 8 weightpercent of the corresponding metal oxide, and the initial pH of said impregnating medium is about 1 to about 2.

5. The method of claim 1 wherein said hydrocarbon feed boils primarily above about 100 F. and contains at least about 50 parts per million nitrogen as organonitrogen compounds and is contacted With said catalyst under hydrogenative denitrogenation condi tions sufficient to reduce the organonitrogen content of said feed by a factor of at least about 50%, and the concentration of said molybdenum compound in said impregnating medium corresponds to at least about 17 weight-percent M00 6. The method of claim 1 wherein said feed boils primarily above about 100 F. and contains at least about 50 parts per million of organonitrogen compounds and is contacted with said catalyst at a temperature of at least about 400 F., a pressure of at least about 500 p.s.i.g. for at least about 1 minute under said superatmospheric hydrogen partial pressure sufiicient to reduce the organonitrogen content of said feed by a factor of at least about 50%.

7. The method of claim 1 wherein said hydrocarbon feed boils primarily above about 400 F. and contains at least about 500 parts per million nitrogen and is contacted with said catalyst at a temperature of at least about 400 F., a pressure of about 500 to about 5000 p.s.i.g. under a superatmospheric hydrogen partial pressure corresponding to an equivalent hydrogen concentration of at least about 50 standard cubic feet of hydrogen per barrel of said hydrocarbon feed for a period of at least about 1 minute suificient to reduce the organonitrogen content of said hydrocarbon by a factor of at least about 50%, and the initial pH of said solution is about 1 to about 2.

8. The method of claim 7 wherein said hydrogenative denitrogenation conditions are sufficient to reduce the organonitrogen content of said feed to less than about 10 parts per million while converting less than 20 relative percent of said feed to hydrocarbon products boiling below the initial boiling point of said feed, said molybdenum compound is ammonium heptamolybdate, said water soluble compound is selected from the nitrates, sulfates, carbonates, hydroxides and chlorides of cobalt and nickel, and the initial pH of said solution is about 1 to about 2.

9. The method of claim 1 wherein said impregnating medium contains an amount of said molybdenum compound equivalent to about 17 to about 24 weight-percent M00 and an amount of said compound of nickel or cobalt corresponding to about 2 to about 8 weight-percent of the corresponding oxide, said 'P/MoO ratio is within the range of about 0.12 to about 0.23, said initial pH is about 1.2 to about 1.8, and said foraminous refractory oxide comprises at least one of silica and alumina.

10. The method of claim 7 wherein said impregnated carrier is aged in contact with said impregnating medium for a period of at least about 30 minutes and said catalytic composition is thermally activated in an oxidizing atmosphere at a temperature of about 800 to about 1300 F. prior to contact with said hydrocarbons.

11. The method of hydrogenatively denitrogenating hydrocarbons containing at least about 50 p.p.m. nitrogen as organonitrogen compounds which comprises reacting said hydrocarbons with hydrogen at a temperature of at least about 400 F., a pressure of at least about 500 p.s.i.g. under a superatmospheric hydrogen partial pressure corresponding to at least about 50 standard cubic feet of hydrogen per barrel of said hydrocarbons for a period of at least about 1 minute sufiicient to reduce the organonitrogen content of said hydrocarbons by a factor of at least about 50% in the presence of a catalytic composition formed on impregnating a foraminous refractory oxide with an aqueous impregnating medium which forms on the admixture of at least one molybdenum compound selected from ammonium heptamolybdate, molybdic oxide, molybdenum trioxide and molybdenum blue, a water soluble compound selected from the nitrates, sulfates, carbonates, hydroxides and chlorides of nickel or cobalt and orthophosphoric acid in proportions equivalent to about 17 to about 30 weight-percent molybdenum trioxide and about 1 to about 10 weight-percent of the corresponding oxide of nickel or cobalt, a P/MoO weight-ratio of about 0.1 to about 0.25 and an initial pH in said aqueous medium of about 1 to about 2 and activating the resultant combination.

12. The method of claim 11 wherein said hydrocarbons boil primarily above about 400 F. and are reacted with said hydrogen at a temperature of about 400 to about 950 F., a pressure of about 500 to about 5000 p.s.i.g. under a superatmospheric hydrogen partial pressure cor- 20 responding to about 400 to about 20,000 standard cubic feet of hydrogen per barrel of said hydrocarbons at a liquid hourly space velocity of at least about 0.4 sufiicient to reduce the organonitrogen content of said hydrocarbons to less than about 10 parts per million.

References Cited UNITED STATES PATENTS 3,617,528 11/1971 Hilfman 208216 3,232,887 2/1966 Pessimissis 252435 3,287,280 11/1966 Colgan et a1. 252435 2,608,534 8/1952 [Fleck 252435 3,609,099 9/1971 Mickelson 252435 3,459,678 8/1969 Hagemeyer, Jr. et al. 252435 3,474,041 10/1969 Kerr 252435 X 3,442,794 5/1969 Van Helden ct a1. 208111 3,684,695 8/1972 Neel et a1. 208110 3,629,146 12/ 1971 Adams 252435 3,686,137 8/1972 Gatti 208254 H DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner US. Cl. X.R. 

